feat: voucher purchase flow

assets/controllers/frame_loading_controller.js

@@ -0,0 +1,26 @@
+import {Controller} from '@hotwired/stimulus'
+
+/*
+ * Shows an indicator over an iframe until its content has loaded.
+ *
+ * The controller sets the frame's src itself, after the load listener is attached, so a fast
+ * response cannot finish before anybody listens.
+ */
+export default class extends Controller {
+    static targets = ['frame', 'indicator']
+    static values = {src: String}
+
+    connect() {
+        this.loaded = this.loaded.bind(this)
+        this.frameTarget.addEventListener('load', this.loaded)
+        this.frameTarget.src = this.srcValue
+    }
+
+    disconnect() {
+        this.frameTarget.removeEventListener('load', this.loaded)
+    }
+
+    loaded() {
+        this.indicatorTarget.classList.add('hidden')
+    }
+}